Archive for
November, 2011

369,629 people died on America’s roads between 2001 and 2009.
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You can zoom around the map using the controls on the left or search for your town using the box on the right – and the key is on the top left. Each dot represents a life

Teachers hate plagiarism more than they hate stepping on puppies and kittens. If there are two students in a class, and one has plagiarized an assignment and one has crushed some puppies and kittens, and the teacher only has time to turn one of them it to the administration, they’ll turn in the plagiarizer.

Physicists from the University of Stuttgart show the first experimental proof of a molecule consisting of two identical atoms that exhibits a permanent electric dipole moment. This observation contradicts the classical opinion described in many physics and chemistry textbooks.

This statement bugs me for two reasons. One is the “contradicts classical opinion” statement, because statements like this usually are a matter of context, and the contradiction occurs when you strip the context. In physics, most equations come with caveats. There are few that apply universally; most are derived under a set of assumptions or meant to apply under specific conditions. However, there are some who try to apply the equations under conditions that violate the assumptions and should not be surprised when the equation fails. And I think this is one of those cases. The “no permanent electric dipole moment” argument is one of symmetry. As long as the symmetry is maintained, there is no EDM, and electrons distributions a these cases should ensure that symmetry. But what happened in this research is a way was found to violate that symmetry — by putting one of the pair of atoms into a Rydberg state (high energy level, maximum angular momentum for the state, which makes the atom physically large). The electron is far from the nucleus and the other electrons can’t compensate. That’s pretty neat, and I think we should celebrate that, rather than the sensationalistic “They said it couldn’t be done!” half-truth.

The other part is the use of “permanent”. This is an excited state. It’s not permanent, though Rydberg states tend to be long-lived. Though that may also be a terminology issue, with permanent simply meaning lives long enough to be measured.

In 2009, to better record crime scenes, the New York City Police Department began using the Panoscan, a camera that creates high-resolution, 360-degree panoramic images. Each panorama takes between 3 to 30 minutes to produce, depending on the available light, and is added to a database where detectives can access it. Before the switch to the Panoscan, crime scene images sometimes took days to process. Now, soon after the photos are posted, investigators can point and click over evidence from a scene that they might have missed in the hectic hours after the crime.

Overall I agree — there are a lot of people who seem to remember the Bohr atom but not that it’s wrong. Unfortunately, some of them seem to want to build their own personal physics theories on it. I understand the motivation to teach it — there is an historical context, and it’s an opportunity to dip one’s toe into some quantum theory rather than jumping into the deep end.

One nit, though. Even thinking of electrons as “buzzing around the nucleus” still implies a trajectory and motion, and you get into trouble trying to reconcile those classical notions with angular momentum, which is one of the failures of the Bohr model: the S orbital has no orbital angular momentum.

I do like the orbital ballon animals, but I don’t recommend a science clown doing them for kids’ parties.

This is a piece created to question whether it was possible to film animation in realtime. Part of my CSM 3rd year disseration project I was looking at proto animation (really early basic animation) in contemporary design.

Brinicles are columns of ice that form under very calm ocean conditions, when there’s a big differential between the water temperature (around -1.9C) and the air temperature about the sea ice (below -20C). The warmer sea flows up to the air, freezing into new ice. According to the BBC, “the salt in this newly formed ice is concentrated and pushed into the brine channels. And because it is very cold and salty, it is denser than the water beneath.” This makes it fall down into the water, creating an ice plume that grows into the brinicle.

When it gets to the ground, it starts to expand, killing everything it touches. The whole process takes five to six hours, according to the team, which is surprisingly fast.

One step better would be an explanation for the inevitable “How does that work?” (or similar) question that arises, so here’s a quick explanation of the physics-y ones. The ping-pong ball tends to stay in the column of air owing to Bernoulli’s principle — pressure decreases the faster the air moves, so there is lateral pressure gradient which gives you a restoring force. The coin and card trick works because the force on the card is probably larger than the force on the coin, and even if they are comparable, card is less massive so it undergoes a much larger acceleration. Consequently, it moves away much faster than the coin, so the coin doesn’t get displaced very far.

Jabbing a sharp pencil through a bag tends to form a hole that conforms to the pencil, and water seals small gaps at low pressure owing to the surface tension. Straws are stronger along their length and covering then end with your thumb means air can’t escape; the increased pressure from the potato being forced into it makes it even stronger against collapsing. Matches burning heat up air and make it expand, so the density is lower than outside. When the matches go out the air cools, lowering the pressure. The egg provides a good seal, and the outside pressure forces the egg inside.

The others have elements of chemistry biology/physiology. So I will pass on those explanations.